Control logic test circuit

ABSTRACT

Means are provided for rapidly, completely, and substantially automatically checking the integrity of the logic and related circuitry employed to control and direct the initiation and termination of combustion at elevations of burners in a furnace. The existing burner control logic is utilized in the generation of substantially all of the input signals to remaining logic under test. The driven devices, such as burner guns, fuel valves, etc., are prevented from responding to their command signals supplied by the control logic. These command signals appearing at the outputs from the control logic system are indicative of proper operation of the logic required to produce them. The feedbacks to the control logic from the sensing devices associated with the driven devices are operative to indicate the fact that the disabled driven devices have not responded correctly to input commands during startup and to effect the necessary commands resulting in a shutdown sequence of the control logic. Means are provided for simulating the two or three signals required for proper sequential operation of the logic which fail to appear when the existing logic is operated in a test mode.

United States Patent 1191 Schuss 1111 3,781,161 1 51 Dec. 25, 1973CONTROL LOGIC TEsT CIRCUIT [75] Inventor: Jack Ascher Schuss, WestHartford,

Conn.

221 Filed: Jan. 3, 1972' [21] Appl. No.: 214,877

[52] US. Cl... 431/16, 431/26, 431/189 [51] Int. Cl. F23n 5/24 [58]Field of Search 431/14, l5, 16, 24, 431/26, 25

[56] References Cited UNITED STATES PATENTS 2,751,972 6/1956 Loeber431/26 3,008,517 11/1961 Pierz 431/16 3,123,027 3/1964 Livingston 110/283,258,053 6/1966 Schuss 431 29 3,684,423 8/1972 Bryant 4.31/24 PrimaryExaminer-Carroll B. Dority, Jr. Attorney-Eldon H. Luther et al.

[5 7 ABSTRACT Means are provided for rapidly, completely, andsubstantially automatically checking the integrity of the logic andrelated circuitry employed to control and direct the initiation andtermination of combustion at elevations of burners in a furnace. Theexisting burner control logic is'utilized in the generation ofsubstantially all of the input signals to remaining logic under test.The driven devices, such as burner guns, fuel valves, etc., areprevented from responding to their command signals supplied by thecontrol logic. These command signals appearing at the outputs from thecontrol logic system are indicative of proper operation of the logicrequired to produce them. The feedbacks to the control logic from thesensing devices associated with the driven devices are operative toindicate the fact that the disabled driven devices have not respondedcorrectly to input commands during startup and to effect the necessarycommands resulting in a shutdown sequence of the control logic. Meansare provided for simulating the two or three signals required for propersequentialoperation of the logic which fail to appear when the existinglogic is operated in a test mode.

11 Claims, 6 Drawing Figures PATENTEUUEE25I975 3381 161 SHEEI 1 0F 4FIG. 2

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CONTROL LOGIC TEST CIRCUIT BACKGROUND OF THE INVENTION A large varietyof processes are controlled using automatic or semi-automatictechniques. Such automated techniques rely upon various nonhuman meansfor implementing the process according to a particular logic pattern.The means comprising and for controlling the system logic may in someinstances be initially defective or may fail at some later time, thusimpairing control of the process.

In many such process control systems economics, time and safety factorswill permit detection and replacement of defective components in arelatively leisurely manner. However in other instances because ofconsiderations of safety and/or the cost of system inoperability, meansmust be provided for maintaining a close check on the integrity of thesystem elements which direct the pattern of operation of the process.

In a system for controlling the combustion of a fuel, as in the furnaceof a large steam generator, it is generally necessary to detect andrepair any defects in the controls as rapidly as possible to preventcostly shutdowns and to insure availability. for startup. In somesituations, certain defects might permit a potentially explosivecondition to be created within a furnace. Control systems exist forautomatically controlling the various driven devices of a burner such asignitors, burner guns, and fuel valves in a manner determined by systemlogic. Generally the driven devices are controlled to initiatecombustion at the burner within a predetermined time span and uponsatisfaction of certain first conditions in response to a start commandand to ter minate combustion within a predetermined time span and uponsatisfaction of certain other conditions in response to a stop orshutdown command. Sensing means determine the state of activity oroperation of the various driven devices and this information is fed backto the logic of the control system. The system logic may include meansfor generating a stop command to effect the combustion terminationprocess when a particular state of activity consistent with combustionis not attained at one or more ofthe driven devices at the expiration ofthe start time span.

The various elements which comprise the control system logic for a steamgenerator, particularly those for controlling initiation and terminationof combustion, have heretofore been tested or checked by simulatingvarious input signals to all or most of the logic elements individuallyand noting the output response 'of each logic element. The actualfeedback signals from controlled or driven devices have beendisconnected so as not to interfere with the multitude of simulatedinput signals. While such a checking arrangement is capable ofaccurately checking all or most of the logic elements, it is quiteexpensive to provide and time consuming to operate. Further, theincreased use of solid state circuitry often does not permit readyaccess to each logic element for testing.

SUMMARY OF THE INVENTION According to the invention, means are providedfor rapidly checking the integrity of the logic and related circuitryemployed to control and direct the operation of the driven devices of asteam generator burner. A control logic checking circuit is providedwhich is relatively simple and inexpensive, is readily adaptable toexisting burner control logic and is particularly suited for use withsolid state logic. The circuit allows automatic exercising of the logicthrough both the combustion initiate or startup mode and the combustionterminate or shutdown" mode as a complete cycle, requiring little timeand a minimum of manual intervention.

The checking circuit of the invention is designed to be operated when aburner and its logic are in a shutdown condition and are not presentlybeing used in the combustion control process. During the checkingoperation the burner in no way contributes to or interferes withexisting conditions of combustion within a furnace. A single switch inthe electrical power circuit to all of the various driven devices of aburner prevents response of the devices to the drive commands occurringat the outputs of the control logic during the test or check mode ofoperation. The feedbacks from the various sensing means associated withthe driven devices continue to provide information to the logic duringoperation in the test mode and indicators activated by the presence ofdrive commands at the control logic outputs inform the operator of theoperability or inoperability of that logic required to provide aparticular drive command. A minimal number of simulated signals arerequired for completely automatic exercising of the control logic in thetest mode. The actual signals generated by individual control and logiccircuits under test are utilized as inputs to other control and logiccircuits being tested, thus minimizing the need for manual simulation ofsignals.

In a preferred embodiment of the invention, the plural burners of afurnace elevation are operated as a unit with both combustion initiationand termination at and by the several burners being accomplished in asequential manner by control logic requiring a single start or stopcommand. The control logic is comprised of low voltage solid statecircuitry and the driven devices are powered by a higher voltage source.The control logic checking circuit requires but a single switch in thehigh voltage power line to all of the driven devices to prevent theirresponse to drive commands and only two or three simulated signals needbe generated for a test sequence in order to have proper automaticsequential exercise of the entire control logic through a completestartup and shutdown cycle.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagramatic illustrationof a vapor generator capable of employing the present invention.

FIG. 1a is a sectional plan view of the vapor generator of FIG. 1 takenalong line la-la.

FIG. 2 is a schematic illustration of a typical automatically operatedburner arrangement according to the invention.

FIG. 3a is a schematic diagram of a portion of the burner control systemof the present invention common to a plurality of burners.

FIG. 3b is a schematic diagram of another portion of the burner controlsystem of the present invention applicable to an individual burner.

FIG. 4 is a schematic diagram of a portion of the burner control systemwhich provides operation in a test mode.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1 there isshown in diagramatic form an elevational section of a vapor generatorhaving a furance chamber 12 in which the invention and its preferredembodiment is designed to operate. A plurality of main burners 14 arearranged in four corners of the chamber 12 for discharging and burningstreams of fuel supplied thereto through a main fuel supply line 16 inthe furnace chamber. In the illustrated embodiment there are threeelevations of burners each consisting of four burners, 14a, 14b, 14c and14d with a burner located at each of the four corners of the furnacechamber 12. The walls of the furnace chamber 12 are lined with vaporgenerating tubes 18 which are in heat exchange relation with combustiongases rising within the furnace chamber 12 and serve to generate andsupply vapor to a load in a well known manner. The amount of vaporcreated in the generator can be grossly controlled by the number ofburners l4 placed in operation to compliment the analog controlsoperating upon the main control valve in the main fuel supply line 16.Generally, the burner elevations are adapted to be operated eithersingly or together depending on the desired generator output.

While the test circuitry of the invention might be described inconnection with control systems for controlling a variety of processes,and particularly in conjunction with controls for the burners in steamgenerating units which employ any of a variety of fuels, such as coal,gas or oil for combustion, the preferred embodiment will describe theinvention in association with the controls for effecting startup andshutdown of an elevation of burners in a vapor generator which uses oilas its principle fuel. The test circuit of the invention is particularlysuited to the burner controls for an oil fired vapor generator becauseof the relatively large number of electrically actuated means directlyassociated with controlling initiation and termination of the combustionprocess at each burner.

Going now to FIG. 2, each fuel burner 14 will be considered as anarrangement including an oil gun 20, a fuel supply conduit 22 whichincludes fuel supply valve 24 connected between the main fuel supplyline 16 and the gun 20, a fluid conduit 26 including valve 28 connectedbetween a purging medium such as steam (not shown) and gun 20, and anignitor torch 30 disposed to ignite fuel issuing from gun 20. A generaldescription of the burner arrangement employed in the preferredembodiment will be provided hereinafter; however, a more detaileddescription of such a burner arrangement may be found in U. S. Pat. No.3,258,053 to Schuss.

Oil gun includes a barrel 32 which is attached to and carried by apiston 34 slidably mounted in cylinder 36. Cylinder 36 is fluidlyconnected to a source of pneumatic power (not shown) by fluid lines 38and 40 and a dual solenoid operated four-way valve 42, the solenoid 44being actuable to admit pneumatic fluid to cylinder 36 behind piston 34to extend barrel 32 of fuel gun 20 to its operable position and solenoid46 being actuable to admit pneumatic fluid to cylinder 36 in front ofpiston 34 to retract barrel 32. Also associated with fuel gun 20 arelimit switches 48 and 50. Limit switch 48 is normally open and thecontacts are closed only when oil gun 20 is fully retracted. Limitswitch 50 is normally open and the contacts are closed only when oil gun20 is fully extended. A flexible fluid conducting sleeve 52 fluidlyconnects gun 20 with fuel conduit 22 and purging conduit 26 throughjunction 54.

Fuel conduit 22 includes a valve 24 in series therewith and operated byoperator 56 which includes motor 58 and solenoid 60. Motor 58, whenenergized, operates to open valve 24 and solenoid 60, when energized,operates to permit closure of valve 24 in a manner described in said U.S. Pat. No. 3,258,053.

Conduit 26 for the purging medium includes valve 28 which is operated byoperator 62 including motor 64 and solenoid 66 which function in thesame manner as for the above described valve 24 and operator 56, Le.motor 64 opens the valve and solenoid 66 closes it. A check valve 67 isinterposed in conduit 26 downstream of valve 28 to assist in preventingfuel backup into conduit 26.

Limit switches 68, and 72 are associated with valve 24 such that thecontacts of switch 68 close only when valve 24 is firlly open, thecontacts of switch 70 are normally closed and open only when the valveis fully open, and the contacts of switch 72 close only when the valveis fully closed.

Limit switches 74 and 76 are associated with valve 28 such that thecontacts of switch 74 are closed only when valve 28 is fully closed andthe contacts of switch 76 are closed only when valve 28 is fully open.

An ignitor torch 30 is associated with each oil gun 20 and is operatedby a separate source of fuel supply (not shown) connected to torch 30 byconduit 77 which includes valve 79. Valve 79 is operated by valveoperator 81 which includes a reversible motor 83. Motor 83 operates toopen valve 79 when lead 85 connecting motor 83 is energized and themotor operates to close valve 79 when lead 87 connecting the motor isenergized. A source of heat, such as spark plug 89, is electricallyconnected to transformer 91 and is excited by energizing conductive lead93 to the transformer. Spark plug 89 ignites torch 30 when the fuelissues from oil gun 20.

In the instant arrangement, an ignitor monitor 78 is operably associatedwith ignitor torch 30 to indicate the torchs ability to supplysufficient ignition energy to ignite the fuel that issues from itsassociated gun 20. The contemplated ignitor monitor 78 is as describedin detail in U. S. Pat. No. 3,123,027 to Livingston. It comprieses apair of pressure taps 80 and 82 which, in association with a pressuredifferentiating chamber 84, measure the pressure differential existingwithin torch 30 at spaced points therealong. This pressure differentialis indicative of the amount of ignition energy the ignitor 30 is capableof delivering.

A Ap switch 86 having output terminals 88 and 90 is arranged such thatwhen less than a predetermined pressure differential is evidenced withinchamber 84 of monitor 78, a contact is closed to complete a circuit tooutput terminal 88 to indicate a condition of insufficient ignitorenergy and when the pressure differential is greater than thepredetermined pressure differential a contact is closed to complete acircuit to output terminal 90 to indicate a condition of sufficientignitor energy.

In the normal operation of most vapor generators an entire elevation ofburners 14 is introduced into or removed from service as load demandrequires. A burner control system employing the checking circuit of theinvention is employed for controlling the startup and shutdown of eachelevation of burners. A separate combustion control system, not formingpart of the invention, is used to modulate fuel and air flow duringcontinuous operation of the burners 14 in an elevation.

FIGS. 3a and 3b are schematic diagrams of burner control system 92 usedto control the startup and shutdown of a burner elevation. Morespecifically, FIG. 3a depicts, in diagramatic form, that part of thecontrol system which is responsible for coordinating and directing thestartup and shutdown procedures for the four burners 14a, 14b, 14c and14d which typically comprise a burner elevation. The control arrangementis such that combustion is initiated or terminated at each of the fourburners in a predetermined sequence. FIG. 3b depicts a portion of theburner control system 92 which is associated entirely with a singleburner, 140, but which is repeated identically in each of the otherthree burners in an elevation. In FIG. 3a, those signals which areassociated only with a particular burner are given the alphabeticalsubscript of the corresponding burner.

Speaking very generally, the startup of a burner 14 to place it inoperation within a furnace 12 requires ignition of torch 30 followed byextension of oil gun 20 and finally, opening of the main fuel valve 24.The ignitor torch 30 may at some later time be extinguished.

The general procedure for shutdown or termination of combustion at aburner 14 includes ignition of torch 30 followed in a sequence byclosure of main fuel valve 24, opening of purge valve 28, closure ofpurge valve 28, and retraction of oil gun 20. The torch 30 is thenextinguished.

The procedure for burner shutdown in the event of a dangerous condition,such as loss of water circulation in vapor generator 10, is termed atrip and generally includes prompt and substantially concurrent extin'guishing of torch 30 and closure of valves 24 and 28 if either is open.

The control circuitry 92 of FIGS. 3a and 3b may be comprisedsubstantially entirely of electro-mechanical control and logic elements,however recent developments in solid state logic suggest a controlsystem employing solid state circuitry, at least to perform the logicfunctions. Solid state components are more compact than relays and thelike and are usually affected to a lesser extent by adverse conditionsof the operating environment. The solid state circuitry generallyoperates at low voltage levels (324V); however various input signals maybe generated from a high voltage supply (1 V). In the instances in whichsignals of different voltages are to be interfaced, a signal convertermay be required to step up or step down the signal voltage. The logicelements of control system 92 operate in a binary digital manner andFIGS. 3a and 3b will be described accordingly. Control system 92 may beviewed as comprising a decision logic section and start and stop commandsignal means for affecting the startup and shutdown exercisesrespectively of the decision logic.

Referring now to FIG. 3a, a signal 94 indicative of remote operationalcontrol is provided as an input to control system 92. Signal 94signifies operation of the burner control system from a remote position,such as a control room, and permits automatic remote exercise orutilization of control system 92. Signal 96 is generated at the abovementioned remote position and permits initiation of individual elevationstartup or shutdown by an operator stationed at the console in thecontrol room.

Signal 98, to be described in greater detail below, serves to lock outor prevent operation of the burners 14 when the control system isexercised in a test mode in accordance with the invention.

It will be noted that the conductors carrying signals 94, 96 and 98, andin fact the remaining signals to be discussed in the case, arethemselves designated 94, 96, 98, etc. respectively. It is felt that thedesignation of conductors by the signals carried is not only economicalof drawing space, but lends clarity to the following description.Throughout the description of the preferred embodiment, it is intendedthat the stated presence of a signal shall mean the existance of adigital signal in the logical 1" state and that a logical 0 is presentat all other times. In the few instances in which a signal is referredto in the logical 0 state, this fact is so indicated.

Start and stop command signals 100 and 102 respectively are the outputsof or gates 104 and 106 respectively. Start and stop command signals 100and 102 respectively are utilized to initiate exercise of the startupand shutdown functions of the control system logic in the automatic andmanual operational modes and in the test mode of the invention. Inroutine remote automatic operation, an automatic start signal 108 isremotely generated and is connected to an input of or gate 104 toprovide start command signal 100. Correspondingly, an automatic stopsignal 110 and remote operation signal 94 are connected to the twoinputs of an and gate 112 to provide signal 114 when signals 94 and 110are concurrently present. Signal 114 is applied as an input to or gate106 to provide stop command signal 102.

In the remote operational mode, remote manual control may be exercisedthrough control system 92. This may be necessitated by inoperability ofthe automatic central control facilities. In such instances, remoteoperation signal 94 and manual mode signal 96 are each applied to two ofthe three inputs to each of and gates 116 and 1 18. Start and stop pushbuttons 120 and 122 generate signals 124 and 126 respectively which arerespectively applied to the remaining input to each of and gates 116 and118. When signals 94, 96 and 124 are present concurrently, the output ofand gate 116 is a signal 128 applied to an input of or gate 104 and whensignals 94, 96 and 126 are present concurrently, the output of and gate1 18 is a signal 130 applied to an input of or" gate 106.

A bistable circuit element, such as flip-flop 131, is used tocharacterize operation of control system 92 in either a startup (orstart) submode or a shutdown (or stop) submode within the earliermentioned major modes. When a start command signal 100 occurs it isapplied to one of the two inputs of flip-flop 131 and is effective toset the flip-flop in one of its two stable states, resulting in anoutput signal 132 which signifies operation in the startup" submode.Correspondingly, when a stop signal 102 occurs, it is applied as aninput to an or gate 134 to provide output signal 136 therefrom which isconnected to the other input of flip-flop 131. Signal 136 is effectiveto reset the flip-flop to its other stable state, resulting in an outputsignal 138 which signifies operation in the shutdown submode.

Start command signal 100 is applied to one of the three inputs of andgate 140, startup submode characterizing signal 132 is connected toanother of the inputs of the and" gate, and an elevation permissivessignal 142 is applied to the remaining input. Elevation permissivessignal 142 exists in the logical 1 state when all general unitpermissive conditions such as furnace purge completed, no boiler trippresent, adequate fuel header pressure available, etc. are satisfied.When signals 100, 132 and 142 are present concurrently, and gate 140provides an output signal 144.

correspondingly, stop command signal 102 is applied to one of the threeinputs of and gate 146, shutdown submode characterizing signal 138 isconnected to another of the inputs of the and gate, and the elevationpermissives signal 142 is applied to the remaining input and an outputsignal 148 therefrom exists when the three input signals are presentconcurrently.

Elevation sequencer and timer 150.is comprised of a plurality of timingcircuits internally programmed to provide various outputs atpredetermined times following application of an input signal 144 or 148.The timing circuits of timer 150 preferably employ solid statecomponents and may be any of several types well known in the art.Therefore, a detailed description of the circuitry internal to timer 150will not be undertaken and instead the various outputs will be describedin a manner which will make evident the characteristics and capabilitiesof timer 150. Typically, timer 150 might include several sequencers orprogrammers such as the Chronologics Model SP101 Programmer, each beingresponsive to or started by one or the other or both of signals 144 and148. Each SP101 Programmer might provide one or several of the signaltime sequences to be described below in response to a start signal, suchas signal 144 or 148. The timing of each output signal provided by aProgrammer will depend on its preset timing.

Sequencer and timer 150 may be divided into a first section 152 which isresponsive to both input signals 144 and 148, to provide output signals154 and 156, a second section 158 which is responsive only to inputsignal 144 to provide output signals 160a, 160b, 1600, 160d and 162, anda third section 164 which is responsive only to input signal 148 toprovide output signals 166a, 166b, 166e, 166d and 168. Each section,152, 158 and 164 of timer 150 might include one or more SP101Programmers. The conductors carrying signals 144 and 148 will beconnected such that both will provide start signals for the Programmeror Programmers forming section 152 of timer 150.

When either signal 144 or 148 is first applied to an input of timer 150,a timing sequence for startup or shutdown respectively of an entireburner elevation is initiated. An ignitor trial time signal 154 existsfor the first seconds following initiation of the sequence. Signal 156appears at 15 seconds and indicates expiration of the ignitor trial timeand continues until initiation of the next ignitor trial time signal154.

If control system 92 is in the startup submode and signal 144 appears asan input to timer 150, burner start signals 160a, 160b, 1600 and 160dwill exist from 15 to 90 seconds, 30 to 90 seconds, 45 to 90 seconds,and 60 to 90 seconds respectively following initiation of the sequence.Signal 162 appears at the output of timer 150 at 90 seconds after signal144 is applied as an input thereto and continues until a new startup orshutdown sequence is attempted in response to a new start or stopcommand signal or 102.

Correspondingly, when the control system 92 is in the shutdown submodeand signal 148 appears as an input to timer 150, burner purge signals166a, 166)), 166C and 166d will exist from 15 to seconds, 30 to 145seconds, 45 to 145 seconds and 60 to 145 seconds respectively followinginitiation of the sequence. Signal 168 appears at the output of timer150 145 seconds after signal 148 is applied as an input thereto andcontinues until a new startup or shutdown sequence is attempted inresponse to a new start or stop command signal 100 or 102.

Each burner start signal and each burner purge signal 166 is responsiblefor initiating burner start and burner purge functions respectively inthe particular burner arrangement 14 associated with the particularsignal in the time sequence in which the signals appear. The ignitortrial time signal 154 is applied to all of the ignitors 30 in anelevation simultaneously as is also the ignitor trial time expiredsignal 156 immediately following termination of signal 154.

A purge valve trip signal 170 is provided as an output from and gate 172upon the concurrent appearance at the two inputs thereof of startupsubmode signal 132 and ignitor trial time signal 154. Purge valve tripsignal 170 is applied simultaneously to all burners in an elevation. 1

A burner trip signal 174 is provided as an output from or gate 176 uponthe appearance at the inputs thereof of either signal 168 or a boilertrip signal 178. Boiler trip signal 178 will be initiated remotelyeither automatically or manually when a speedy termination of thecombustion process is desired or required. Burner trip signal 174 isapplied simultaneously to all burners in an elevation. Additionally, anignitor trip signal 180 is provided as an output from or gate 182 uponthe appearance at the inputs thereof of either signal 168, or boilertrip signal 178, or ignitors off signal 184. The ignitors off signal 184is provided by a manually actuated push-button 186 which may be utilizedat any time an ignitor trip is desired. Ignitor trip signal 180 isapplied simultaneously to all ignitors 30 in an elevation.

Referring now to FIG. 3b, the logic circuitry associated with aparticular burner arrangement 14 (e.g. 14a) is shown. Signal 88 arisesfrom A P switch 86 when insufficient ignitor energy is present. Signal88 is applied to one of the two inputs associated with each of and gates188 and 190. Ignitor trial time signal 154 is applied to the other inputto and gate 190 and ignitor trial time expired signal 156 is applied tothe other input to and gate 188. Signal 192 results as an output fromand gate 190 when insufficient ignitor energy exists to ignite fuelissuing from fuel gun 20 and the ignitor trial time occur concurrently.Correspondingly, a signal 194 results as an output from and gate 188when insufficient ignitor energy exists and the ignitor trial time hasexpired.

Signal 192, when applied to flip-flop 196, sets the flip-flop to a stateproviding an output signal 198. Both ignitor trip signal 180 and signal194 are applied as inputs to or gate 200, resulting in an output signal202 when either is present. Signal 202 when applied to the other inputof flip-flop 196 resets the flip-flop to provide an output signal 204.Signal 204 is used as an indication of ignitor off. When signals 198 and154 appear concurrently as inputs to and gate 206, an output signal 208results therefrom. Signal 208 is present during the seconds whichignitor trial time signal 154 exists if ignitor 30 is not producingsufficient ignition energy. Signal 198 is also applied as one of the twoinputs of and gate 210. Signal 212 is the output from inverter 214 andis applied to' the other input of and gate 210. Signal 212 will be inthe logical l state only when signal 88 is not present as a logical 1input to inverter 214. Therefore, signal 212 is indicative of acondition of sufficient ignitor energy. The output from and gate 210 isasignal 216 which signifies an ignitor on condition.

Signals 204,208 and 154 represent output signals from control system 92and are employed to direct the opening and closing of valve 79 in thefuel supply conduit 77 to ignitor torch 30 and the excitation oftransformer 91. Signal 204 acts, through means such as AC switch 218, tobe described in greater detail below, to provide a motor driving ACpotential to lead 87. A limit switch 220, not previously shown, isconnected in series with lead 87 between AC switch 218 and motor 83.Limit switch 220 is normally closed and is associated with valve 79 insuch a manner that it is opened only when the valve is closed. Thus,when signal 204 is present as an output from control system 92 and,through AC switch 218 and limit switch 220, applies an AC drivingpotential to lead 87, the motor will be energized to close valve 79.Signal 208 is also an output from control system 92 and is applied to ACswitch 222 Signal 208 acts through switch 222 to provide an AC drivingpotential to lead 85 which in turn is applied to motor 83 to open valve79. Normally closed limit switch 224, not previously shown, is locatedin series with lead 85 and is associated with valve 79 such that it isopened only when the valve is fully open.

Signal 154 also is present as an output from control system 92 and isapplied to AC switch 226 to provide an AC energizing potential to lead93 connected to the primary of ignitor transformer 91.

As with the ignitor 30 associated with a burner arrangement, the otherdriven devices making up the burner also respond to output signals fromcontrol system 92. An output signal 236 from control system 92 .isapplied to AC switch 238 and acts to apply an AC driving voltage tosolenoid 44 through lead 239 to extend fuel gun 20. Correspondingly, anoutput signal 240 from control system 92 is applied to AC switch 242 andacts to apply an AC driving voltage tov solenoid 46 through lead 243 toretract fuel gun 20.

Output signal 244 from control system 92 is applied to AC switch 246 andacts'to apply an AC driving voltage to solenoid 60 through'le'ad 247 toclose fuel valve 24. Correspondingly, output signal 248 is applied to ACswitch 250 and acts to apply an AC driving voltage to motor 58 throughlead 251 toopen the fuel valve. A normally closed limit switch 252, notpreviously shown, is placed in series with the AC voltage supply tomotor 58 and is adapted to be opened only when fuel valve 24 is fullyopen.

Output signal 254 from control system 92 is applied I to AC switch 256and acts to apply an AC driving voltage through lead 257 to solenoid 66to close burner purge valve 28. Correspondingly, output signal 258 isapplied to AC switch 260'and acts to apply an AC driving voltage throughlead 261 to motor 64 to open the burner purge valve. A normally closedlimit switch 262,

not previously shown, is placed in series with the AC voltage supply tomotor 64 and is adapted to be opened only when purge valve 28 is fullyopened.

The limit switches associated with fuel gun 20, fuel valve 24, and purgevalve 28 have been previously described and the conductors which carrythe resulting logic signals to the decision logic of control system 92are designated by the primed designation for the corresponding limitswitches and will, as hereinbefore, be used to indicate the existance ofa digital signal in the logical 1 state. In this embodiment, the logical1 signal state occurs when the associated switch is closed.

The burner arrangement depicted in FIG. 3b has arbitrarily been chosenas that of burner arrangement 14a and accordingly receives burner startsignal a and burner purge signal 166a. A local control switch 228a isassociated with each particular burner arrangement, in this instanceburner 14a, and may be manually controlled to provide signal 230a when arapid shut down of the burner is desired or signal 234a when a locallyinitiated purge of 14a is intended. Signal 232a is provided when remoterather than local control of the burner is required.

An and gate 264 has connected thereto, as inputs, burner start signal160a, signal 74' indicative of a closed burner purge valve, signal 232aindicating remote operation of burner arrangement 14a, and signal 266which is the output from or" gate 268. Signal 216 which signifies anignitor on condition is applied as an input to or gate 268 to providesignal 266. The output of and gate 264 is a signal 270 which existswhile, concurrently, the burner purge valve is closed, an indication ofignitor on exists, local control switch 228a permits remote operationand a burner start signal 160a for this burner arrangement 14a exists.

Signal 270 is connected as one of the two inputs to and gate 272, theother input being signal 274. Signal 274 is the output of an inverter276 which has as its input signal 50 from limit switch 50. Signal 274exists in the logical l state when a logical 0 is present at the inputto the inverter 276 or, in other words, when switch 50 is open andsignal 50' is in a logical 0 state. When both signals 270 and 274 arepresent as inputs to and gate 272,, control system output signal 236results as the output therefrom.

Signal 270 is also applied as one of the three inputs to and gate 278,the other two inputs being signals 280 from or gate 282 and signal 284from inverter 286. Signal 50 is connected as an input to or gate 282 toprovide output signal 280 when fuel gun 20 is extended and limit switch50 is closed. Signal 284 is the inverse of signal 288 discussed belowand applied as the input to inverter 286. The output of and gate 278,signal 292, when first applied to an input of flip-flop 294 sets theflip-flop to a state which provides, as an output therefrom, controlsystem output signal 248. Signal 288 is also connected to the otherinput of flipflop 294 and, when occurring, resets the flip-flop toprovide, as an output, control system output signal 244.

The output signal 288 from or gate 290 results when either one of thetwo signals 304 and 306 is present at the input to the gate. Signal 306is the output of or gate 308 which has as its inputs burner purge signal166a and local purge signal 234a. Signal 304 is the output of or gate310 which has as its inputs burner trip signal 174, locally generatedtrip signal 230a and signal 312. Signal 312 is the output of and gate314 which has as its three inputs remote signal 94, signal 204indicating an ignitor off condition and signal 70' which exists wheneverfuel valve 24 is not fully open.

Signal 306, which is required to effect purging of the burner, isapplied as one of the five inputs to and gate 316. The remaining fourinputs to the and gate are signals 266, 280, 72' and 318. Signal 318 isthe output of inverter 320 which has as its input, control system outputsignal 254. Signal 254 is provided by or gate 324 having as inputs,purge valve trip signal 170, signal 304, and signal 326 described below.

Control system output signal 240 which commands the retraction of fuelgun 20 is the output of and gate 334. The two inputs to and gate 334 aresignals 74' and 326. Signal 74 will exist during such time as burnerpurge valve 28 is closed and signal 326 occurs as an output fromflip-flop 336. Flip-flop 336 is set to the state which provides signal326 when signal 338 is first applied to an input thereof and is resetwhen signal 304 is applied to the other input thereof. Signal 338, whichsets flip-flop 336, is the output from time delay element 340. Delayelement 340 is of the type which provides a logical 1 signal at itsoutput some delayed time, here 60 seconds, following the appearance of alogical 1 signal at the input thereto. The output of element 340 goesimmediately to the logical state when the logical l at the input isreplaced by a logical 0. The input to delay element 340 is the outputsignal 339 from or gate 337. An input to or gate 337 is provided bysignal 76' from limit switch 76. Signal 339 will appear as a logical 1when purge valve 28 is fully open. Thus, set signal 338 appears at theinput to flip-flop 336 some 60 seconds following full opening of purgevalve 28.

The various stages of actuation or positioning of ignitor 30, burner gun20, fuel valve 24, and purge valve 28 are indicated by the varioussensing means, such as the A P switch and the limit switches, associatedtherewith. These indications may function as permissives, required as aprerequisite to actuation of a particular portion of the burnerarrangement and they may also function to indicate failure of aparticular driven device to achieve a desired state. Signal 70, whichindicates that its associated fuel valve 24 is not open, is applied asan input to an inverter 342 to provide output signal 344. Signal 344 isthen in the logical 1 state when the fuel valve is open and serves as anindication of such.

Referring back to FIG. 3a, signals 344a, 344b, 344s and 344d, eachindicative of a fuel valve open condition are applied as inputs to aconventional 2 out of 4 voting circuit 346. Voting circuit 346 is of atype which provides a logical 1 output signal 348 whenever at least twoout of the four input signals are in the logical l state. Another way ofstating it, signal 348 exists when at least two of the four fuel valves24 in an elevation are indicated as being open.

Signal 348 may be used to signify that an elevation is in service if anindication that 2 out of 4 fuel valves are open is established as beingdeterminative of elevation operation. However, the condition of the fuelvalves at the end of the startup sequence has also been selected as ameans for indicating unsuccessful startup and signal 348 is applied toinverter 350 to provide an output signal 352 which is in the logical 1state whenever at least 3 out of 4" of the fuel valves are not open.

As 2 out of4 fuel valves open indicates that an elevation is properly inservice, signal 352 indicating at least 3 out of 4 fuel valves not beingopen is utilized to initiate shutdown of the elevation. Signal 352,signal 162 indicating the lapse of seconds in the startup sequence, andsignal 132 indicating operation in the startup submode are applied asthe three inputs to and gate 353 to provide output signal 355. Signal355 then will appear at the end of the startup sequence if three or fourof the fuel valves have not opened. Signal 355 is applied as an input toflip-flop 357 and its appearance thereat sets the flip-flop, providingoutput signal 359 therefrom. Signal 359 is thus indicative of anunsuccessful startup and acts through amplifier 361 to energize an alarmor annunciator 363.

Signal 359 additionally acts in a known manner through time delayinverter 365 and and gate 367 to provide a signal 369 which isrelatively short in duration and is indicative of the unsuccessfulstartup. Signal 369 appears as a pulse and is applied as one of theinputs to or gate 106 responsible for initiating the shutdown sequence.Flip-flop 357 is reset by the appearance of signal 371 at its otherinput. Signal 371 is an output from or gate 373, one input to which isthe manually generated start signal 124.

Signals indicating the ignitor off condition from each of the individualignitors 30 in an elevation and signals indicative of the fuel valveclosed condition from each individual fuel valve 24 in an elevation arealso fed back to control system 92 for indication and control purposes.Signals 204a, 204b, 2040, and 204d, each indicative of the ignitor offcondition of an ignitor in the elevation, are applied to the four inputsof and gate 354 to provide an output signal 356 when all four ignitorsare off. Signals 72a, 72b, 72c and 72d, each indicative of the fuelvalve closed condition of a fuel valve in the elevation, are applied tothe four inputs of and gate 358 to provide an output signal 360 whenfour fuel valves are closed.

Both signals 356 and 360 are provided as the two inputs to and gate 362providing an output signal 364 when all of the fuel valves are closedand all of the ignitors are off. Signal 364 is further applied to aninverter 366 and inverted to provide output signal 368 which will appearin the logical l state at any time one or more of the ignitors is notoff or the fuel valves are not closed. Signals 368 and 168 are appliedas the two inputs to and gate 370 which provides an output signal 372when, in the shutdown submode, seconds have elapsed since the start ofthe shutdown sequence and at least one of the ignitors remains on or oneof the fuel valves remains open. Signal 372 is applied to an amplifier374 and the amplified signal acts to energize an alarm or annunciator376.

Thus far, a control system and associated burner elements have beendescribed which provide for remote automatic or manual startup andshutdown of the burners within an elevation of burners in a furnace.Also described as part of the control system have been means forinitiating automatic shutdown of the entire elevation in the event of anunsuccessful startup. The test circuit of the invention, to be describedhereinafter, provides means for completely and automatically exercisingthe logic of control system 92 substantially as hereinbefore described.Indicators, activated by each of the control system output signals 204,208, 154, 236, 240, 244, 248, 254 and 258 associated with each burner inan elevation, provide an indication of whether or not a particularcontrol system output signal does in fact occur as an output fromcontrol system 92. If activation of an indicator fails to occur whenexpected, it is taken as an indication of a failure in the controlsystem prior to that point in the sequence and conventional, analyticalrepair techniques may be employed to correct the defect. However, theaforementioned exercising of control system 92 for circuit testingpurposes will normally be undertaken when the particular elevation ofburners associated therewith is not in service. Under thesecircumstances, it is desirable that the logic of system 92 beexercisable but that the driven elements of a fuel burner arrangement 14be prevented from operating in response to the control system outputsignals. According to the invention, a control system test circuit isprovided which permits exercise of the control system in a naturalmanner without actuating the driven devices associated with a burner.The existing logic is utilized to generate input signals to subsequentlogic under test with a minimum of signal simulation and humanparticipation.

When it is desired to perform a test of the circuitry of control system92, the particular elevation of burners associated therewith will beplaced in the shutdown condition. A lock-out switch 378, seen in FIG. 4,is associated with each elevation of burners in furnace 10. This switchwill normally be located in proximity to the circuitry of control system92 and not necessarily in the central control location. Switch 378 iscomprised of a single pole double throw switch having terminals 380,382, and 384. An AC supply voltage (typically 115V) is connected toterminal 380. Terminal 382 will be connected to ground and terminal 384is connected with an output conductor 386. When the contacts of switch378 close the circuit between terminals 380 and 384, the AC potential isapplied to conductor 386 and when the contacts close the circuit betweenterminals 382 and 384 output conductor 386 will be at ground potential.The position of switch'378 in which the AC potential is applied toconductor 386 has been termed the remote position and the position whichgrounds conductor 386 has been termed the lock-out position.

Conductor 386 is connected to a signal conditioner 388 which converts anAC voltage to a low voltage DC signal as required for the logic elementsof control systern 92. The output of signal conditioner 388 is remotesignal 94, previously mentioned. Remote signal 94 will be in the logical1 state when switch 378 is in the remote position and in the state whenit is in the lock-out position. Signal 94 is connected as an input toinverter 390'to provide an output signal 98 which is a logical I whenswitch 378 is in the lock-out position and is a logical 0 when theswitch is in the remote position. Signal 98 may be referred to as thelock-out or test mode signal.

Conductor 386 also serves as the AC power supply bus to the variousactuators associated with the driven devices of all of the burners 14a,14b, 14c and 14d in an elevation. However, for the sake of brevity, onlysolenoids 44 and 46 which control actuation of a particular fuel gun 20have been shown in FIG. 4. Solenoids 44 and 46 are connected in parallelcircuits between AC supply conductor 386 and a conductor 392 at groundpotential. AC switches 238 and 242 are respectively connected in eacharm of the parallel circuits having solenoids 44 and 46. A separate ACswitch is associated with each of the actuators 44 and 46 and likewisewith the other actuators not shown in FIG. 4.

AC switches 238 and 242 are ofa type which will respond to thepresence-of an enabling command signal, such as control system outputsignal 239 or 243, or the remaining system output signals not shown inFIG. 4, to close the circuit which provides AC driving potential acrossa particular one of the actuators. Each AC switch includes a gatedswitch element, such as triac 396, connected in series with an actuatorsuch as solenoid 44 and the source of AC power at conductor 386. When aswitching potential is applied to the control electrode 398 of triac 396the triac will conduct, closing the power supply circuit to solenoid 44and when the switching potential is removed the triac will ceaseconducting and open the power supply circuit. This arrangement permitsuse of the low voltage DC control system output signals to control theswitching of triac 396 and accordingly energization or de-energizationof the various actuators such as solenoid 44. AC switches 238 and 242,as depicted in FIG. 4, utilize a low voltage relay 400 actuated by acontrol system output signal such as 239 to close a contact 402 betweencontrol electrode 398 and the source of switching potential provided byresistor 404. The presence at the output of control system 92 of acommand signal such as signal 239 is indicated by means such as lowvoltage lamp 406 connected in parallel with relay 400. When controlsystern output signal 239 is present, a low voltage DC energizingpotential is applied across lamp 406 to provide an indication of signalpresence. It will be recognized that various other means may be used tosignify and/or record the presence of the output signal.

The startup sequence for a burner elevation is as follows. A startcommand signal sets the submode characterizing flip-flop 131 to thatstate indicating operation in the startup submode and providing signal132. Substantially simultaneously and assuming the elevation permissivesare satisfied as indicated by signal 142, signal 144 is provided as aninput to sequencer and timer which provides the output signals requiredto start ignitor 30 and to extend the fuel guns 20 and open fuel valves24 associated with the various burners l4. Signal 154 is applied to eachignitor torch 30 in the elevation simultaneously and serves to ignitethe several torches by concurrently opening fuel valves thereto andexciting the spark transformers 91. At 15 seconds each of the severalignitor torches 30 is examined through its respective and gate 188 todetermine whether sufficient ignitor energy is present to ignite thefuel issuing from fuel gun 20. If there is insufficient ignitor energyat, say, the ignitor for burner 14a, signal 216 will not appear as alogical l and, accordingly, the and gate 264 will be prevented orinhibited from passing burner start signal a. If, as is usually thecase, sufficient ignitor energy is present, it is so indicated by signal216 and the startup sequence continues. Each burner 14a, 14b, 14c and14d then receive' output signal 236 to extend fuel gun and uponextension of the fuel gun as indicated by signal 50', acts through andgate 278 and flip-flop 294 to provide control system output signal 248which commands opening of the fuel valve 24. Upon complete execution ofthese commands, initiation of combustion will be effected at each burnerand automatically throughout the entire elevation of burners.

The orderly shutdown of the burner elevation will occur either inresponse to an intentionally generated stop command signal or as theresult of an indication that startup was not successfully initiatedwithin the time period allotted. 1n the preferred embodiment, the latterindication is provided by signal 355 when flipflop 131 is set in thestartup submode, the startup time period has elapsed as indicated bysignal 162, and signal 352 is present to signify that at least three outof four (3 out of 4) fuel valves did not open. It will be realized thatsignals provided by monitoring other driven devices such as the fuel gun20 may serve to indicate failure of the complete startup operation. Stopcommand signal 102 sets flip-flop 131 to the shutdown submodesubstantially simultaneously and, assuming the elevation permissives aresatisfied, signal 148 is provided as an input to sequencer and timer 150which provides the output signals required to start ignitors 30, closefuel valves 24, open and close purge valves 28, and retract fuel guns20. lgnitor start signal 154 is provided as in the startup submode andconcurrently energizes all of the ignitors 30 in the elevation.Beginning 15 seconds after the appearance of ignitor start signal 154and continuing for 130 seconds thereafter, burner purge signals 166a,166b, 1660 and 166d appear in sequence beginning 15 seconds after theappearance of ignitor start signal 154 and continue until 145 secondsafter the appearance of signal 154. A burner purge signal 166 providessignal 306 which first acts through flip-flop 294 to provide controlsystem output signal 244 to close fuel valve 24 and upon an indicationby signal 72' that the fuel valve is closed and an indication by signal280 that fuel gun 20 is extended and an indication by signal 266 thatignitor 30 is on", signal 306 acts through and gate 316 to providecontrol system output signal 258 which opens purge valve 28. Some periodof time following the opening of purge valve 28 as determined by timedelay element 340, flip-flop 336 provides signal 326. Signal 326 firstacts through or gate 324 to provide control system output signal 254which directs closing of purge valve 28 and upon closing of the purgevalve 28, as indicated by signal 74, signal 326 acts through and gate334 to provide control system output signal 240 which directs theretraction of fuel gun 20. At this point, combustion will have beenterminated at each burner and automatically in sequence throughout theentire elevation of burners resulting in burner and elevation shutdownwith the various flip-flops reset for subsequent startup.

When it is desired to perform a test of the logic incorporated incontrol system 92, the test will be initiated manually. Exercise of thelogic will start from a condition in which a particular elevation ofburners is completely shutdown and inactive. Principally, the testprovides an automatic exercise of the logic through the complete startupand shutdown submodes. Means are also provided for initiating theshutdown submode of operation in the test mode in the event of a controllogic failure in the startup logic. This shutdown capability is requiredonly to reset the several flip-flops for a subsequent startup. In eitherevent, some indication that the driven devices of the elevation are inthe shutdown condition will be required prior to initiating the testmode exercise. Accordingly, when switch 378 is placed in the lock-out"position to provide lockout signal 98, a check is made to ascertainwhether or not the elevation is in fact shutdown. Signal 98 is appliedas one of the two inputs to and gate 408 with the other input beingprovided by signal 364. As previously described, signal 364 occurs whenall of the fuel valves and all of the ignitors are off, this being takenas an indication that the elevation is shutdown. The output of and gate408 is a signal 410 which indicates elevation shutdown in the lock-outtest mode and is applied as one of the two inputs to each of the and"gates 412 and 414 to permit a test to be initiated.

Signals 98 and 368 are applied as the two inputs to and gate 428 whichprovides an output signal 430 when both inputs are in the logical 1state. Signal 368 appears as a logical 1 whenever any one of the fuelburner valves or ignitors associated with all of the burners of theelevation is not in a shutdown or off condition. Signal 430 complementssignal 410 in the test mode and will typically be connected to anindicator, not shown, to advise the operator that a test of the logicmay not be conducted at the present time.

Push button 416, when actuated, provides test start pulse signal 418applied to the other input of and gate 414. Push button 420, whenactuated, provides a test stop pulse signal 422 applied to the otherinput of and gate 412. The output of and gate 414 is a signal 424 whichis applied to an input of or gate 104 to provide a control system startsignal 100. The output of and gate 412 is a signal 426 which is appliedto an input of or gate 106 to provide a control system stop signal 102.Additionally, a signal 424 is applied as an input to or gate 373 toreset flip-flop 357 following a possible unsuccessful startup attempt.

Start and stop command signals 100 and 102 respectively, though nowgenerated in the test mode of operation rather than remote or manual,serve to initiate the burner elevation startup and shutdown sequences inessentially the same manner as described above. The remaining logic incontrol system 92 utilized in the startup submode of operation isexercised as described above to provide control system output signals154, 208, 236 and 244. The occurrence of these output signals will beindicated by indicating lamps 406 associated with the corresponding ACswitches. However, because control system 92 is being exercised in thetest or lock-out mode, lock-out switch 378 will have been placed in thatposition which grounds conductor 386. Conductor 386, it will berecalled, is that which normally supplies AC driving potential to thevarious driven devices. The grounding of conductor 386 removes the ACpotential needed for actuation of the various driven elements of theignitor 30, fuel gun 20, burner valve 24 and purge valve 28. Thus, thesedriven elements are incapable of responding to their correspondingoutput command signals and remain in a shutdown or stop" condition.

Because the driven devices required to initiate combustion at theburners of the elevation have been prevented from responding to theircommand signals, their associated limit switches will also fail to moveto the state directed by the command signals. This results in anindication by signal 352 that at least three out of four (and in factfour out of four) of the fuel valves 24 have not opened at theexpiration of the startup submode trial period and in turn results insignal 355. Signal 355 acts through flip-flop 357 to indicate theunsuccessful startup attempt and to generate a stop pulse 369 which actsthrough or gate 106 to provide stop command 102.

Upon the occurrence of stop command 102, the logic of control system 92will then be exercised through a routine shutdown operation resulting incontrol system output signals 154, 204, 248, 258, 254 and 240. Becausethe control system is in the test mode, and the AC switches have beengrounded, these output command signals are incapable of directing theapplication of an AC energizing potential to the corresponding drivendevices. At this point, a complete startup and shutdown exercise of thecontrol logic will have been performed and control system 92 isavailable, with flipflops reset, for a subsequent startup command ineither the test mode or an operational mode.

The exercise of the logic of control system 92 through the startup andshutdown submodes in the test mode of operation is accomplished withsubstantially only that circuitry required to effect a burner elevationstartup and shutdown sequence in the remote automatic or manualoperational modes. However, certain signals are provided only aftercertain of the driven devices have in fact responded to their commandsignals and the inability of these driven devices to respond in the testmode require that their response, or rather a signal indicative ofexpected response, be simulated.

Need for simulated signals occurs at or gates 268, 282, and 337. Each ofthese or gates normally provides an output signal in the logical l stateupon response of some driven device to its associated command signal. Orgate 268 provides signal 266 as an input to and gate 264 when signal 216indicates that the ignitor 30 is on. Or gate 282 provides signal 280 asan input to and gates 278 and 316 when limit switch signal 50 indicatesthat fuel gun 20 is fully extended. Or gate 337 provides signal 339which ultimately sets flip-flop 336 a delayed time following the openingof purge valve 28, as indicated by limit switch signal 76. In eachinstance, the output signal of these or gates is required for continuingthe startup or shutdown sequence. Accordingly, signals which simulatethe occurrence of the required inputs to the three mentioned or gatesare provided and applied to the or gates for use in the test mode ofoperation.

Test mode or lock-out signal 98 is in the logical 1 state for theduration of the test mode and is therefore used for the simulation ofthe required inputs to the above mentioned or gates during the testmode. Signal 98 is applied as an input to both or gates 268 and 280. Inderivinga signal for simulating signal 76, lock-out signal 98 andcontrol system output signal 258 are applied as the two inputs to andgate 432 to provide, as the output therefrom, signal 434 which isapplied as an input to or gate 337. Signal 434 exists during the testmode only when signal 258 is present. This latter provision insures thatsignal 338 is not continuously present as an input to flip-flop 336 sothat signal 304 may reset the flip-flop when it occurs. Signal 258normally directs the opening of purge valve 28,

and accordingly the closing of limit switch 76 to provide signal 7 6.Therefore, it is in the correct time position in the operationalsequence to aid in the simulation of signal 76'. In the instance of thesimulated signals applied to or gates 268 and 282, the continuedpresence of signal 98 as an input throughout the startup and shutdownsubmodes in no way interferes with the proper functioning of theremaining logic.

Thus it will be seen that a complete exercise of the logic of controlsystem 92 can be executed in the test mode and provide a complete checkof the logic with but a minimum of human intervention and changes in thecircuitry.

It will be understood that the embodiment shown and described herein ismerely illustrative and that changes may be made without departing fromthe scope of the invention as claimed.

What is claimed is:

1. In a system for controlling a fuel burner arrangement having aplurality of electrically actuated means for initiating and forterminating a combustion process, control means adapted to function inan operational mode and in a test mode and responsive in both said modesto a start command for automatically providing in a predeterminedsequence at outputs thereof a plurality of commands for actuating saidcombustion process initiating means and responsive in both said modes toa stop command for automatically providing in a predetermined sequenceat outputs thereof a plurality of commands for actuating said combustionprocess terminating means; means for generating said start command;means for generating said stop comstart command; means for selectivelydirecting operation of said system in a said operational mode or in asaid test mode including means for preventing actuation of saidcombustion initiating and terminating means in response to theircorresponding said actuating signals in said test mode; and means forindicating the presence of said actuating commands at the said outputsof said control means whereby the integrity of said control means isverified.

2. The apparatus of claim 1 including sensing means for providingsignals indicative of the response of said combustion initiating andterminating means to their corresponding said actuating commands; andsaid control means include means for providing a signal indicative ofunsuccessful initiation of combustion when said sensing means indicatesa response inconsistent with combustion initiation upon expiration of apredetermined period of time following generation of said start commandand wherein said stop command generating means are responsive to saidsignal indicative of unsuccessful initiation of combustion to generate asaid stop command in said operational mode and in said test mode.

3. The apparatus of claim 2 wherein each of said means for actuatingsaid combustion initiation and combustion terminating means includes anelectrically responsive actuator and each of said actuators is connectedto a source of energizingelectrical power by a series circuit whichincludes said actuator, first switch means adapted for closing when thecorresponding said actuating command is present at an output of saidcontrol means and opening when the corresponding said actuating commandis absent and second normally closed switch means adapted to open whensaid control means are operated in said test mode, thereby preventingactuation of said combustion initiation and terminating means.

4. Apparatus of claim 2 wherein said fuel burner arrangement has amovable fuel gun, a fuel supply valve, a burner purge valve and anignitor torch; said electrically actuated means for initiating and forterminating a combustion process comprise electrically actuated fuel gunmoving means adapted to extend and to retract said gun upon command, anelectrically actuated fuel supply valve operator adapted to open and toclose said fuel supply valve upon command, an electrically actuatedburner purge valve operator adapted to open and to close said burnerpurge valve upon command and electrically actuated means for ingitingand for extinguishing said ignitor torch upon command; and said sensingmeans utilized for indicating a response inconsistent with initiation ofcombustion include means for indicating the operative position of saidfuel supply valve, said fuel supply valve being required to be open forinitiation of combustion.

5. The apparatus of claim 4 wherein said fuel burner arrangementincludes a plurality of fuel guns and associated fuel supply valves,burner purge valves and ignitor torches; said control means includemeans for providing said actuating commands to each of the plurality offuel gun moving means and associated burner purge valve operators, fuelsupply valve operators and ignitor torch igniting and extinguishingmeans in a predetermined sequence in response to said start and stopcommands; said fuel supply valve position sensing means are associatedwith each of said plurality of fuel supply valves; and means responsiveto said indications of fuel supply valve operative positions providesaid signal indicative of unsuccessful initiation of combustion when amajority of said fuel supply valves are not opened.

6. The apparatus of claim 4 wherein said sensing means further includeignition sensing means associated with said ignitor torch for providinga signal indicative of the state of ignition of said ignitor torch; saidcontrol means include first means for providing said command to extendsaid fuel gun and said command to open said fuel valve only uponreceiving a sig nal indicating ignition of said ignitor torch; andincluding means for simulating said signal indicating ignition of saidignitor torch when said control means are operated in said test mode,said simulated signal being connected to said first means.

7. The apparatus of claim 6 wherein said sensing means further includegun position sensing means associated with said fuel gun and purge valveposition sensing means associated with said burner purge valve forproviding, respectively, signals indicative of .the operative states ofsaid fuel gun and said purge valve; said control means include secondmeans for providing said command to retract said gun only upon receivinga sig nal indicating extension of said gun and third means for providingsaid command to close said purge valve only upon receiving a signalindicating said purge valve as open; and including means for simulatingsaid signals indicative of the fuel gun extended and purge valve openconditions when said control means are operated in said test mode, saidsignals being connected to said second and third means, respectively.

8. A system for controlling a fuel burner arrangement having a movablefuel gun, a fuel supply valve, a burner purge valve and an ignitortorch; electrically actuated fuel gun moving means adapted to extend andto retract said gun upon command; an electrically actuated fuel supplyvalve operator adapted to open and to close said fuel supply valve uponcommand; an electrically actuated burner purge valve operator adapted toopen and to close said burner purge valve upon command; electricallyactuated means for igniting and for extinguishing said ignitor torchupon command; sensing means including fuel valve position sensing meansfor providing a signal indicative of the operative position of said fuelsupply valve; decision logic means adapted to function in an operationalmode and in a test mode and having means responsive to a start commandfor generating a signal indicative of operation in a start-up submodeand responsive to a stop command for generating a signal indicative ofoperation in a shutdown submode, means responsive to said start commandfor generating a signal indicative of a predetermined time span for saidstartup submode, means responsive to said stop command for generating asignal indicative of a predetermined time span for said shutdownsubmode, means for providing within said startup time span in responseto said start command and in a predetermined sequence at respectiveoutputs of said decision logic means a command signal to ignite saidignitor torch, a command signal to extend said fuel gun and a commandsignal to open said fuel supply valve and for providing within saidshutdown time span in response to said stop command and in apredetermined sequence at respective outputs of said decision logicmeans a command signal to close said fuel supply valve, a command signalto open said burner purge valve, a command signal to close said burnerpurge valve, a command signal to retract said fuel gun and a commandsignal to extinguish said ignitor torch, and logic means responsive tosaid indication of fuel valve position, said indication of said startupsubmode and said indication of said startup time span for providing anoutput signal indicative of an unsuccessful start when said fuel valveis not open at the expiration of said startup time span in said startupsubmode; means for generating said start command; means responsive to atleast said signal indicative of an unsuccessful start for generatingsaid stop command; switch means responsive to operation of said decisionlogic means in said test mode for preventing actuation of said fuel gunmoving means, said ignitor torch actuating means, said fuel valveoperator and said purge valve operator in response to theircorresponding command signals; and means for indicating the presence ofsaid command signals at their respective said outputs of said decisionlogic means whereby the integrity of said logic is verified.

9. The apparatus of claim 8 wherein said sensing means further includeignition sensing means associated with said ignitor torch, gun positionsensing means associated with said fuel gun and purge valve positionsensing means associated with said burner purge valve for providing,respectively, signals indicative of the state of ignition of saidignitor torch, the operative state of said fuel gun and the operativestate of said purge valve; said decision logic means inclue first,second, and third logic means for, respectively, providing said commandsignal to extend said fuel gun and open said fuel valve only uponreceiving a signal indicating ignition of said ignitor torch, providingsaid command signal to retract said gun only upon receiving a signalindicating extension of said gun, and providing said command signal toclose said purge valve only upon receiving a signal indicatingsaid purgevalve as being open; and including means for simulating said signalsindicative of the ignited state of said ignitor torch, the extendedposition of said gun and the valve open position of said purge valvewhen said decision logic means are operated in said test mode, saidsimulated signals being respectively connected as inputs to said first,second and third logic means.

10. The apparatus of claim 8 wherein said fuel gun moving means includesfirst and second electrically responsive actuators for advancing andretracting respectively said fuel gun; said fuel supply valve operatorincludes third and fourth electrically responsive actuators for openingand closing respectively said fuel supply valve; said burner purge valveoperator includes fifth and sixth electrically responsive actuators foropening and closing respectively said burner purge valve; said ignitortorch igniting and extinguishing means includes seventh and eighthelectrically responsive actuators for igniting and extinguishingrespectively said ignitor torch; and each of the said eight electricallyresponsive actuators is connected to a source of electrical power by aseries circuit which includes said electrically responsive actuators,first switch means adapted for closing when a corresponding saidactuating command is present at an output of said decision logic meansand for opening when the corresponding said actuating command is absentand second normally closed switch means adapted to open when saiddecision logic means are operated in said test mode for preventingresponse of said actuator to its corresponding command.

11. The apparatus of claim 8 wherein said indicating means comprise: anelectrically energized light source associated with each of saiddecision logic means command signal outputs; means connecting each saidlight source to a supply of electrical energy; and each said connectingmeans including switch means in series therewith for closing the circuitto said light when the corresponding command signal is present at itscorresponding output of said logic means.

1. In a system for controlling a fuel burner arrangement having aplurality of electrically actuated means for initiating and forterminating a combustion process, control means adapted to function inan operational mode and in a test mode and responsive in both said modesto a start command for automatically providing in a predeterminedsequence at outputs thereof a plurality of commands for actuating saidcombustion process initiating means and responsive in both said modes toa stop command for automatically providing in a predetermined sequenceat outputs thereof a plurality of commands for actuating said combustionprocess terminating means; means for generating said start command;means for generating said stop comstart command; means for selectivelydirecting operation of said system in a said operational mode or in asaid test mode including means for preventing actuation of saidcombustion initiating and terminating means in response to theircorresponding said actuating signals in said test mode; and means forindicating the presence of said actuating commands at the said outputsof said control means whereby the integrity of said control means isverified.
 2. The apparatus of claim 1 including sensing means forproviding signals indicative of the response of said combustioninitiating and terminating means to their corresponding said actuatingcommands; and said control means include means for providing a signalindicative of unsuccessful initiation of combustion when said sensingmeans indicates a response inconsistent with combustion initiation uponexpiration of a predetermined period of time following generation ofsaid start command and wherein said stop command generating means areresponsive to said signal indicative of unsuccessful initiation ofcombustion to generate a said stop command in said operational mode andin said test mode.
 3. The apparatus of claim 2 wherein each of saidmeans for actuating said combustion initiation and combustionterminating means includes an electrically responsive actuator and eachof said actuators is connected to a source of energizing electricalpower by a series circuit which includes said actuator, first switchmeans adapted for closing when the corresponding said actuating commandis present at an output of said control means and opening when thecorresponding said actuating command is absent and second normallyclosed switch means adapted to open when said control means are operatedin said test mode, thereby preventing actuation of said combustioninitiation and terminating means.
 4. Apparatus of claim 2 wherein saidfuel burner arrangement has a movable fuel gun, a fuel supply valve, aburner purge valve and an ignitor torch; said electrically actuatedmeans for initiating and for terminating a combustion process compriseelectrically actuated fuel gun moving means adapted to extend and toretract said gun upon command, an electrically actuated fuel supplyvalve operator adapted to open and to close said fuel supply valve uponcommand, an electrically actuated burner purge valve operator adapted toopen and to close said burner purge valve upon command and electricallyactuated means for ingiting and for extinguishing said ignitor torchupon command; and said sensing means utilized for indicating a responseinconSistent with initiation of combustion include means for indicatingthe operative position of said fuel supply valve, said fuel supply valvebeing required to be open for initiation of combustion.
 5. The apparatusof claim 4 wherein said fuel burner arrangement includes a plurality offuel guns and associated fuel supply valves, burner purge valves andignitor torches; said control means include means for providing saidactuating commands to each of the plurality of fuel gun moving means andassociated burner purge valve operators, fuel supply valve operators andignitor torch igniting and extinguishing means in a predeterminedsequence in response to said start and stop commands; said fuel supplyvalve position sensing means are associated with each of said pluralityof fuel supply valves; and means responsive to said indications of fuelsupply valve operative positions provide said signal indicative ofunsuccessful initiation of combustion when a majority of said fuelsupply valves are not opened.
 6. The apparatus of claim 4 wherein saidsensing means further include ignition sensing means associated withsaid ignitor torch for providing a signal indicative of the state ofignition of said ignitor torch; said control means include first meansfor providing said command to extend said fuel gun and said command toopen said fuel valve only upon receiving a signal indicating ignition ofsaid ignitor torch; and including means for simulating said signalindicating ignition of said ignitor torch when said control means areoperated in said test mode, said simulated signal being connected tosaid first means.
 7. The apparatus of claim 6 wherein said sensing meansfurther include gun position sensing means associated with said fuel gunand purge valve position sensing means associated with said burner purgevalve for providing, respectively, signals indicative of the operativestates of said fuel gun and said purge valve; said control means includesecond means for providing said command to retract said gun only uponreceiving a signal indicating extension of said gun and third means forproviding said command to close said purge valve only upon receiving asignal indicating said purge valve as open; and including means forsimulating said signals indicative of the fuel gun extended and purgevalve open conditions when said control means are operated in said testmode, said signals being connected to said second and third means,respectively.
 8. A system for controlling a fuel burner arrangementhaving a movable fuel gun, a fuel supply valve, a burner purge valve andan ignitor torch; electrically actuated fuel gun moving means adapted toextend and to retract said gun upon command; an electrically actuatedfuel supply valve operator adapted to open and to close said fuel supplyvalve upon command; an electrically actuated burner purge valve operatoradapted to open and to close said burner purge valve upon command;electrically actuated means for igniting and for extinguishing saidignitor torch upon command; sensing means including fuel valve positionsensing means for providing a signal indicative of the operativeposition of said fuel supply valve; decision logic means adapted tofunction in an operational mode and in a test mode and having meansresponsive to a start command for generating a signal indicative ofoperation in a start-up submode and responsive to a stop command forgenerating a signal indicative of operation in a shutdown submode, meansresponsive to said start command for generating a signal indicative of apredetermined time span for said startup submode, means responsive tosaid stop command for generating a signal indicative of a predeterminedtime span for said shutdown submode, means for providing within saidstartup time span in response to said start command and in apredetermined sequence at respective outputs of said decision logicmeans a command signal to ignite said ignitor torch, a command signal toextend said fuel gun and a command signal tO open said fuel supply valveand for providing within said shutdown time span in response to saidstop command and in a predetermined sequence at respective outputs ofsaid decision logic means a command signal to close said fuel supplyvalve, a command signal to open said burner purge valve, a commandsignal to close said burner purge valve, a command signal to retractsaid fuel gun and a command signal to extinguish said ignitor torch, andlogic means responsive to said indication of fuel valve position, saidindication of said startup submode and said indication of said startuptime span for providing an output signal indicative of an unsuccessfulstart when said fuel valve is not open at the expiration of said startuptime span in said startup submode; means for generating said startcommand; means responsive to at least said signal indicative of anunsuccessful start for generating said stop command; switch meansresponsive to operation of said decision logic means in said test modefor preventing actuation of said fuel gun moving means, said ignitortorch actuating means, said fuel valve operator and said purge valveoperator in response to their corresponding command signals; and meansfor indicating the presence of said command signals at their respectivesaid outputs of said decision logic means whereby the integrity of saidlogic is verified.
 9. The apparatus of claim 8 wherein said sensingmeans further include ignition sensing means associated with saidignitor torch, gun position sensing means associated with said fuel gunand purge valve position sensing means associated with said burner purgevalve for providing, respectively, signals indicative of the state ofignition of said ignitor torch, the operative state of said fuel gun andthe operative state of said purge valve; said decision logic meansinclue first, second, and third logic means for, respectively, providingsaid command signal to extend said fuel gun and open said fuel valveonly upon receiving a signal indicating ignition of said ignitor torch,providing said command signal to retract said gun only upon receiving asignal indicating extension of said gun, and providing said commandsignal to close said purge valve only upon receiving a signal indicatingsaid purge valve as being open; and including means for simulating saidsignals indicative of the ignited state of said ignitor torch, theextended position of said gun and the valve open position of said purgevalve when said decision logic means are operated in said test mode,said simulated signals being respectively connected as inputs to saidfirst, second and third logic means.
 10. The apparatus of claim 8wherein said fuel gun moving means includes first and secondelectrically responsive actuators for advancing and retractingrespectively said fuel gun; said fuel supply valve operator includesthird and fourth electrically responsive actuators for opening andclosing respectively said fuel supply valve; said burner purge valveoperator includes fifth and sixth electrically responsive actuators foropening and closing respectively said burner purge valve; said ignitortorch igniting and extinguishing means includes seventh and eighthelectrically responsive actuators for igniting and extinguishingrespectively said ignitor torch; and each of the said eight electricallyresponsive actuators is connected to a source of electrical power by aseries circuit which includes said electrically responsive actuators,first switch means adapted for closing when a corresponding saidactuating command is present at an output of said decision logic meansand for opening when the corresponding said actuating command is absentand second normally closed switch means adapted to open when saiddecision logic means are operated in said test mode for preventingresponse of said actuator to its corresponding command.
 11. Theapparatus of claim 8 wherein said indicating means comprise: anelectrically energized light source associated with each of saiddecisIon logic means command signal outputs; means connecting each saidlight source to a supply of electrical energy; and each said connectingmeans including switch means in series therewith for closing the circuitto said light when the corresponding command signal is present at itscorresponding output of said logic means.